(Reuters) - McDonald s Corp reported better-than-expected global sales at established restaurants in May, helped by strong demand in China, but sales in the United States continued to fall.

McDonald s, which has not reported a gain in U.S. comparable -store sales since October, said sales in the United States fell 1 percent in May. Analysts polled by Consensus Metrix had expected sales to rise 0.1 percent.

The United States accounted for 31 percent of McDonald s revenue in 2013. The company does not break out sales for China.

McDonald s shares were down 0.2 percent in trading before the bell on Monday.

The fast-food giant has been struggling in its home market, where sluggish job and wage growth are constraining spending.

But the company is also facing stiff competition from resurgent rivals such as Wendy s Co and Burger King Worldwide Inc as well as dealing with frequent and noisy protests from its minimum-wage workers and its own missteps.

The company introduced several new items, such as sandwich wraps and lattes, last year that required longer times to prepare and slowed service.

The world s biggest restaurant chain by revenue said worldwide sales at restaurants open at least 13 months rose 0.9 percent last month. Analysts had expected a gain of 0.8 percent.

In Europe - the chain s top region, accounting for 40 percent of revenue - same-restaurant sales rose 0.4 percent, short of the 0.5 percent rise analysts had expected.

In the Asia-Pacific, Middle East and Africa region, which includes China, same-store sales rose 2.5 percent - far better than the average market forecast of 0.7 percent.

McDonald s shares were trading at 1.82 about an hour before the market open. Up to Friday s close, the stock had risen 5 percent this year.